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4.6L engine knock after new belt tensioner

Nick Bionda

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The engine was knocking about 3 weeks ago and it was determined the belt tensioner failed so i changed that. I didn’t change the belt at that time. Now a few weeks later the engine is knocking but I can’t ID where it’s coming from. Its definitely a knock (not a tick/lifter) and is present at idle and while driving, but is inconsistent in intensity. Any suggestions on where to start to diagnose?
 


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IPcamper

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Well if you think it was related to the belt and tensioner before, check each idler pulley, alternator, power steering pump, etc to make sure they are all good. If the noise is still coming from the front of the engine, there is the possibility is a timing chain guide has cracked and the chain is slapping the timing cover housing. There are plenty of possibilities, and you will need to locate where it is coming from. A cheap mechanic's stethoscope can help locate the noise. https://www.amazon.com/Mechanics-Diagnostic-Stethoscope-Sonarscope-Listening/dp/B005GRGR7C
 




Nick Bionda

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The engine was knocking about 3 weeks ago and it was determined the belt tensioner failed so i changed that. I didn’t change the belt at that time. Now a few weeks later the engine is knocking but I can’t ID where it’s coming from. Its definitely a knock (not a tick/lifter) and is present at idle and while driving, but is inconsistent in intensity. Any suggestions on where to start to diagnose?
Well if you think it was related to the belt and tensioner before, check each idler pulley, alternator, power steering pump, etc to make sure they are all good. If the noise is still coming from the front of the engine, there is the possibility is a timing chain guide has cracked and the chain is slapping the timing cover housing. There are plenty of possibilities, and you will need to locate where it is coming from. A cheap mechanic's stethoscope can help locate the noise. https://www.amazon.com/Mechanics-Diagnostic-Stethoscope-Sonarscope-Listening/dp/B005GRGR7C
Well if you think it was related to the belt and tensioner before, check each idler pulley, alternator, power steering pump, etc to make sure they are all good. If the noise is still coming from the front of the engine, there is the possibility is a timing chain guide has cracked and the chain is slapping the timing cover housing. There are plenty of possibilities, and you will need to locate where it is coming from. A cheap mechanic's stethoscope can help locate the noise. https://www.amazon.com/Mechanics-Diagnostic-Stethoscope-Sonarscope-Listening/dp/B005GRGR7C
Just to clarify there was a knock present before the tensioner was changed. It was determined the failed tensioner was the cause of the knock and replaced. A new knock has now surfaced after about 3 weeks after the tesioner was replaced.
 




blabla

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Pop the belt off. Start it and listen. Dont run it more than a couple minutes.
 




Nick Bionda

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Once the belt is off what conclusions am I looking for? If it still has the knock/or not what does each mean?
 




Nick Bionda

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Plus isn't that an OHC motor? Won't it affect the cams or timing or anything if I run the motor with the serp belt off?
 




IPcamper

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The serpentine belt dives, the water pump/clutch fan, the power steering pump, the alternator, and the AC. The idler pulleys help route the belt. Their bearings can go bad, but usually sounds like a ticking or grinding sound. You can run the engine for a short time with out the serpentine belt to isolate the noise. Just don't run it for more a couple minutes since the water pump won't be turning and cooling the engine. If you still hear the knocking with the belt off, then you know it is not the accessories on the outside of the engine. If the knocking stops then you need to figure which pulley / accessory is causing the noise.

The 4.6l V8 has two timing chains. The timing chains have plastic guides that can and do wear out. When this happens, one of the chains can sometimes slap the inside of the timing cover on the front of the engine. You also can sometimes hear the chain rattle when the engine first starts up. To confirm that the chains are loose, you can remove the valve covers and look down the timing chains and check to see if they have lost tension.

The mechanic's stethoscope can be used to listen to the engine at specific points. With the engine running touch the probe to different places on the engine and try to find where the knocking is the loudest. This will help you locate the source of the noise.
 




Nick Bionda

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The serpentine belt dives, the water pump/clutch fan, the power steering pump, the alternator, and the AC. The idler pulleys help route the belt. Their bearings can go bad, but usually sounds like a ticking or grinding sound. You can run the engine for a short time with out the serpentine belt to isolate the noise. Just don't run it for more a couple minutes since the water pump won't be turning and cooling the engine. If you still hear the knocking with the belt off, then you know it is not the accessories on the outside of the engine. If the knocking stops then you need to figure which pulley / accessory is causing the noise.

The 4.6l V8 has two timing chains. The timing chains have plastic guides that can and do wear out. When this happens, one of the chains can sometimes slap the inside of the timing cover on the front of the engine. You also can sometimes hear the chain rattle when the engine first starts up. To confirm that the chains are loose, you can remove the valve covers and look down the timing chains and check to see if they have lost tension.

The mechanic's stethoscope can be used to listen to the engine at specific points. With the engine running touch the probe to different places on the engine and try to find where the knocking is the loudest. This will help you locate the source of the noise.
Great input thank you. I’ll be running through this tomorrow morning. Fun.
 




SyberTiger

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How many miles on the engine? And, do you know the full history of the vehicle?

Likely you should expect the timing chains to need service after 120k to 150k miles. Some folks have had the loose chains slap against the timing chain cover and wear a hole thru causing oil to leak out.

Also, consider the harmonic balancer could be the source of the sound ... Maybe it's the vibration that causes the sound like THIS.
 




blabla

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So what did you discover?
 




Nick Bionda

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Pretty sure it’s the lower timing chain guide driver’s side. I was able to pull it off the fitting on the block and put it back on pretty sure there’s supposed to be a bolt that fastens the guide to the block. I just wanna be at least 98% sure before I tear into this huge job. 1st vid is the guide, 2nd is engine running with the noise. The noise is up high and in the front of the motor. I videos of the noise and of the loose guide but can’t figure out how to post them.
 




IPcamper

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I have done the timing chains and components on both a 2002 and a 2003 4.6l V8. It is not that hard. Here is a link to a PDF with a the official procedure for the job. http://www.jegs.com/InstallationInstructions/300/397/397-M-6004-462V.pdf

Many have said that you need to lock the camshafts and the crank in position with special tools. It can be done with out them, but it is harder to torque the camshaft bolts without the tool. To remove the chains without the special tools, rotate the engine by hand until the crankshaft timing mark is at the bottom (6 o'clock) position and the camshaft timing marks are close to the top of the cam gear. ( see diagrams in the link above ) The passengers side camshaft will be under tension, before loosening the bolt, put a large wrench ( 18mm I believe ) on the camshaft bolt and hold the shaft in place while the chain is removed. Then let the camshaft slowly rotate counterclockwise until it stops. Don't let it turn freely or the valves will smack a piston head. when you place the new chain on, set the marked link on the crankshaft in the proper location, and then using the wrench rotate the passenger side camshaft clockwise until the proper chain link can be set on the gear's timing mark. The driver's side camshaft should not be under tension , but use the same precaution of holding the camshaft bolt with a wrench to insure it will not free turn by itself.

As long as the timing marks on the engine line up with the marked links on the chain, your timing will be good.

I work slow at this stuff, it took me about 18 hours the first time I did it, and about 12 hours the second time. You will find you have more clearance to work if you remove the alternator and the water pump. To save your knuckles and the radiator fins, cover the radiator with a large sheet of cardboard.
There are a number of posts and pictures on this forum of this job done by others, the search function is your friend.
 




Nick Bionda

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I have done the timing chains and components on both a 2002 and a 2003 4.6l V8. It is not that hard. Here is a link to a PDF with a the official procedure for the job. http://www.jegs.com/InstallationInstructions/300/397/397-M-6004-462V.pdf

Many have said that you need to lock the camshafts and the crank in position with special tools. It can be done with out them, but it is harder to torque the camshaft bolts without the tool. To remove the chains without the special tools, rotate the engine by hand until the crankshaft timing mark is at the bottom (6 o'clock) position and the camshaft timing marks are close to the top of the cam gear. ( see diagrams in the link above ) The passengers side camshaft will be under tension, before loosening the bolt, put a large wrench ( 18mm I believe ) on the camshaft bolt and hold the shaft in place while the chain is removed. Then let the camshaft slowly rotate counterclockwise until it stops. Don't let it turn freely or the valves will smack a piston head. when you place the new chain on, set the marked link on the crankshaft in the proper location, and then using the wrench rotate the passenger side camshaft clockwise until the proper chain link can be set on the gear's timing mark. The driver's side camshaft should not be under tension , but use the same precaution of holding the camshaft bolt with a wrench to insure it will not free turn by itself.

As long as the timing marks on the engine line up with the marked links on the chain, your timing will be good.

I work slow at this stuff, it took me about 18 hours the first time I did it, and about 12 hours the second time. You will find you have more clearance to work if you remove the alternator and the water pump. To save your knuckles and the radiator fins, cover the radiator with a large sheet of cardboard.
There are a number of posts and pictures on this forum of this job done by others, the search function is your friend.
Thanks that is some very helpful info. I’m not a mechanic but mechanically inclined and the more of this I do the more confident I get. “My old man, is a TV repairman, he has this ultimate set of tools. I can fix it.”
 




blabla

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The trick with the timing marks is to set them once and then believe they are good. Cause once you turn the motor they will never line up again. I know it sounds strange, but that is why I called it a "trick".
 




Nick Bionda

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So I finally finished this job. I found a broken guide and replaced it along with the other guides and tensioners. Put it all back together and started it up and still had the same knocking sound. Exact same sound. I didn’t replace the chains or check/set timing. Ugh.
 




Drewmcg

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I don't have experience with that engine, but your last post makes it sound like you suspect bad timing. However, if the timing is bad, there should either be (i) driveability concerns (you have not stated any); or at least (ii) OBD II errors/indications (e.g., missing cylinders on one bank; out of wack fuel trims). Do you have an OBD reader?
 




Nick Bionda

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Yes it is iding rough, wanting to die a bit, and seems to have a bit of power loss. I will put an OBD II reader on tomorrow and see if I can get some codes.
 




Joe in NY

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have you cleaned out your IAC ?
 






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Nick Bionda

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What’s the OBD scanner on and pull a code that told me had a bad oil on one of the cylinders. Found the coil and it was just loose because the retainer clip is broken. So now the idling rough problem is resolved but the engine knock is still there. Had a Ford mechanic friend take a listen and he said to pull the valve cover off again to check to see if one of the followers came loose and is laying inside the I had somewhere. Possibly also a lifter stock open, but he seems to think that the knocking is pretty deep maybe a rod. UGH.
 




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